This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
USSD was originally developed for GSM. The unstructured supplementary service data (USSD) mechanism allows the Mobile Station (MS) user and a PLMN operator defined application to communicate in a way which is transparent to the MS and to intermediate network entities. The USSD mechanism allows for the development of operator and 3rd party specific supplementary services.
There are two modes of USSD: MMI-mode and application mode. MMI-mode USSD is for the transparent transport of MMI (Man Machine Interface) strings entered by the user to the network and for the transparent transport of text strings from the network that are displayed by the mobile for user information.
Application mode USSD is for the transparent transport of data between the network and the UE (User Equipment). Application mode USSD is intended to be used by applications in the network and their peer applications in the UE.
USSD communications over the radio interface uses short dialogues with peak data throughput rate capabilities of up to approximately 600 bits/s outside of a call and 1000 bits/s during a call.
USSD may be initiated by the MS user, or by the network (i.e., an application server). Unlike Short Message Service (SMS) messages, USSD messages create a real-time connection during a USSD session. The connection remains open, allowing a two-way exchange of a sequence of data. Several examples of how USSD Services are used include: Pre-paid balance Inquiry, Balance Transfer (payment from one's balance to another balance), Voting (“Please rate our customer service: 1=Good, 2=OK, 3=Bad” after a call to a CSR), and Call Me (requesting another party to call you). A USSD Gateway is used to proxy the USSD messaging between the MS user or the UE and the application server providing the service (e.g., a mobile banking application server providing a checking account balance to the MS user).
CDMA USSD service is presently being developed by 3GPP2 (3rd generation Partnership Project 2). There is no existing solution for how to route a CDMA MS USSD initiated request to a USSD Gateway.